The present embodiments relate to a gradient coil arrangement for a magnetic resonance tomography device.
Magnetic resonance devices (e.g., an MR device) for examining patients using magnetic resonance tomography systems are, for example, known from DE10314215.
Modern magnetic resonance systems (MRT) work with coils for emitting high-frequency pulses for nuclear resonance excitation and/or for receiving induced magnetic resonance signals. A magnetic resonance system may include a permanent magnet or a superconducting coil for generating a basic magnetic field (HO) that is as homogeneous as possible in an examination area, and may include a large body coil that may be permanently incorporated into the MR device and multiple small local coils (e.g., surface coils or LC). To read out information, from which images of a patient may be generated, selected regions of the object or patient to be examined may be read out with gradient coils for three axes (e.g., X and Y axes approximately radial to the patient and a Z axis in a longitudinal direction of the patient). The spatial encoding in the magnetic resonance tomography system may be realized with the aid of a gradient coil arrangement with three independently controllable, magnetically orthogonal gradient field coil systems (e.g., three freely scalable fields). By overlaying the three freely scalable fields (in three directions X, Y, Z), the orientation of an encoding plane (“gradient field”) may be freely selected.
Gradient field coils may be operated with high currents and large steady-state power dissipations and are therefore cooled. Because the field efficiency depends on the radius of the field-generating coils, the three conductor-bearing regions (X, Y, Z) provided are fitted on top of and close to one another. To dissipate large amounts of heat, at least one cooling plane directly adjacent to the gradient coils is fitted onto or between the regions.
In the case of thin-walled (e.g., approximately 70 mm thick) gradient coils, an approximately 4 mm thick cooling layer may be incorporated for each of the three primary and secondary gradient axes.
A coil body may be manufactured, for example, from an epoxy resin mass of high electric strength that, in a vacuum casting procedure, fills all hollow spaces of the concentric layer structure of the (gradient) coil sections. The casting compound fills radial gaps between the wire ranges that are advantageous for achieving the electric strength.
Wires for the structure of the transverse coils (X, Y) are fixed on level GRP carrier plates and rolled cylindrically. The GRP carrier plates have a high mechanical strength and support the isolation strength between two adjacent gradient axes even if no casting compound penetrates into the radial gap. The wires for gradient coils for the Z axis are cylindrically wound onto one of the GRP carrier plates. A cooling layer is either built up of metallic, electrically conductive structures or of non-metallic, electrically isolating structures.